In 3GPP long-term evolution advanced (3GPP LTE-A) technology, the relay technology is adopted. The relay is a technology that processes and forwards received signals by a relay node to thereby expand radio coverage and enhance data throughput. The relay technology may improve the coverage of high data rate, group mobility, temporary network deployment and the throughput of a cell edge, and may also be used to provide the coverage in new areas. With the relay technology, a relay node (RN) divides a direct link from a base station (eNB) to a user equipment (UE) with a relatively poor quality into two links with relatively good qualities, i.e., an access link and a backhaul link, where the access link refers to the link between the RN and the UE, and the backhaul link refers to the link between the eNB and the RN.
The relay node is wirelessly connected to the radio access network via a donor cell (namely, the cell supporting the relaying). With regard to the relay node's spectrum usage, the operation of the relay node can be divided into:                inband, in which case the eNB-RN link shares the same carrier frequency as RN-UE links. Rel-8 UEs should be able to connect to the donor cell in this case.        outband, in which case the eNB-RN link does not operate in the same carrier frequency as RN-UE links. Rel-8 UEs should be able to connect to the donor cell in this case.        
As is well known, the “Type 1” relay node as defined in 3GPP TR36.814 V9.0.0, is an inband relay node, characterized by:                It controls cells, each of which appears to a UE as a separate cell distinct from the donor cell;        The cells shall have their own Physical Cell IDs (defined in LTE Rel-8) and the relay node shall transmit its own synchronization channels, reference symbols, and etc.        In the context of single-cell operation, the UE shall receive scheduling information and HARQ feedback directly from the relay node and send its control channels (SR/CQI/ACK) to the relay node;        It shall appear as a Rel-8 eNB to Rel-8 UEs (i.e. be backwards compatible); and        To LTE-Advanced UEs, it should be possible for a relay node to appear differently than Rel-8 eNB to allow for further performance enhancement.        
Because the above “Type 1” relay node is an inband relay node, the backhaul link and the access link will use the same frequency band and thus the relay transmitter will cause interference on its own receiver. Therefore, it is infeasible for the backhaul link transmission and the access link transmission are performed simultaneously on the same frequency resource, unless sufficient isolation of outgoing signals with incoming signals is provided, for example, by means of specific, well separated and well isolated antenna structures.
One possible solution for handling the above interference problems is to operate the relay so that the RN is not transmitting data to the user equipment when it is supposed to receive data from the donor eNB (DeNB, an eNB supporting the relaying). In other words, “gaps” are created in an access link transmission. During these gaps, the RN will not transmit any information to the UE. These gaps, for example, may be created through configuring MBSFN subframes as illustrated in FIG. 1. As illustrated in FIG. 1, the RN-UE transmission uses a common subframe (as illustrated at the left side), while the eNB-RN transmission employs an MBSFN subframe (as illustrated in the right side). The transmission between eNB and RN will be facilitated by not allowing transmission between RN and UE within some subframes.
Thus, some subframes in a downlink radio frame are configured as the backhaul subframes for transmission from the DeNB to RN, while the other subframes are access subframes for transmission from the RN to the UE. Different macro cells often use different backhaul subframes configurations and thus, it is required to carefully design interference estimation and channel measurement in an environment wherein different backhaul subframes configuration are used in different macro cells, such that the measured channel quality matches the actual interference condition.
In the US patent publication US2010/0080139A1 filed on Sep. 28, 2009, there are disclosed techniques for supporting relay operation in a wireless communication systems. Based on the technical solution as disclosed in this patent application, the eNB will generate a bitmap that indicates the subframe configuration in multiple radio frames, wherein the bitmap may indicate the type of each subframe in radio frames, i.e., whether it is an MBSFN subframe or a normal subframe, or is a blank subframe or a normal subframe; the eNB transmits the generated bitmap to the UE; the UE, based on the type of the subframe as indicated by the bitmap, performs channel estimation or measurement for the normal subframe, but skips the channel estimation or measurement for the blank subframe or MBSFN subframe.
FIG. 2 schematically illustrates an interference model commonly used in LTE-A standardization community, wherein the desired signals during the downlink access subframes and the backhaul subframes are illustrated with solid lines and long dotted lines, respectively, and the interference signals during the access subframes and the backhaul subframed are illustrated with short dotted lines and chain dotted line respectively. During the backhaul subframes as illustrated with long dotted lines, the eNB may also schedule data for the macro UE (MUE) besides scheduling data for the RN; and the interference in the backhaul subframes mainly comes from eNBs. On the other hand, during the access subframes as illustrated with solid lines, the RN transmits data for the relay user equipment (RUE), and meanwhile eNBs also transmit data for respective MUEs. In this case, the interference in these access subframes comes from both RNs and eNBs.
As illustrated in FIG. 2, the interference may come from a neighboring cell. However, in actual application, the backhaul subframes configurations in respective neighboring cells may be different for various factors such as different traffic condition of each cell. Thus, the technical solution as proposed in the US patent may not work well in this case, due to measurement mismatch with the actual interference condition. Therefore, there is a need for a technical solution suitable for this condition in the art.